The wavelength of laser {in nanometers} for shaping cornea in refractive surgery is-
**Core Concept**
The question is testing the knowledge of laser technology used in corneal refractive surgery, specifically the wavelength required for shaping the cornea. This involves understanding the principles of laser-tissue interaction and the specific application of excimer lasers in ophthalmology.
**Why the Correct Answer is Right**
Excimer lasers are used in corneal refractive surgery to reshape the cornea, and the most commonly used wavelength is 193 nanometers (nm). This wavelength is chosen because it has a high absorption coefficient in the corneal tissue, allowing for precise removal of corneal tissue without causing significant thermal damage. The 193 nm wavelength is also well-absorbed by the corneal collagen, which helps to minimize the risk of thermal damage and promote a smooth, even surface.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it is not the correct wavelength used for corneal refractive surgery. Although other wavelengths may be used in ophthalmology, 193 nm is the specific wavelength used for excimer laser refractive surgery.
* **Option B:** This option is incorrect because it is not a commonly used wavelength in ophthalmology. While some lasers may operate at this wavelength, it is not specifically used for corneal refractive surgery.
* **Option C:** This option is incorrect because it is not the correct wavelength used for corneal refractive surgery. This wavelength may be used in other medical applications, but it is not the standard for excimer laser refractive surgery.
**Clinical Pearl / High-Yield Fact**
The excimer laser is a non-ablative laser, meaning it does not remove tissue through thermal damage, but rather through photochemical reactions that break the molecular bonds in the corneal tissue. This allows for precise removal of corneal tissue with minimal thermal damage.
**Correct Answer:** C. 193 nanometers.